There is an ever-increasing requirement for photographing using a mobile phone. However, when a photographing environment is a low illumination scenario, for example, luminance of the environment is less than 30 lux, for example, in a cinema, a pub, or a KTV, if there is no other auxiliary equipment, because light in the environment is extremely low and there is a small amount of light admitted into a camera, a photographed image is dark, and a clear and distinguishable image cannot be photographed.
To resolve this problem, some manufacturers add a camera flash to a rear-facing camera of a mobile phone to improve a photographing effect in a low light environment. However, during photographing, the camera flash usually dazzles human eyes, and a case in which user eyes temporarily cannot clearly see an object appears. In addition, a soft light function is added to front-facing cameras of some mobile phones, and when photographing is performed, a front-facing soft light is turned on to increase luminance in an environment. However, the light is relatively dazzling after being turned on, and a case in which user experience is not ideal also appears. In addition, a manufacturer uses a light emitting diode (LED) fill-in light solution to instantly increase luminance of a screen when photographing is performed. A problem of this manner is that there is no effect on previewing, and as a distance between a user and a mobile phone changes, a problem such as face asymmetry, ineffective brightening, or overexposure is caused when photographing is performed.